For example, data centers in which a plurality of electronic devices are installed (telephone base stations, infrastructure facility control device machine rooms, or the like) play a role as an information infrastructure. Furthermore, due to globalization, in order to operate devices stably in countries or regions in which they are never used, it is necessary to diagnose corrosiveness of installation environments of devices in a short period of time. In emerging countries among such countries, since the emerging countries are located at low latitudes, it is estimated that relative humidity is high, and a lot of corrosive gas is emitted. According to a report by ASHRAE, in the data center, a failure that an electrode material of a chip part (a small resistor, capacitor, thermistor, or the like for surface mounting) corrodes due to reducing sulfur (for example, hydrogen sulfide) contained in corrosive gas frequently occurs.
In order to suppress corrosive damage of such electronic parts, it is desirable to diagnose corrosiveness of an installation environment, improve an air conditioning facility before a failure occurs due to corrosion of an electronic part, and replace the electronic part.
As a method of diagnosing the corrosiveness of the installation environment, in ASHRAE of NPL 1, a method of measuring a corrosion thickness of silver or copper, calculating an average corrosion progression from the corrosion thickness and an exposure period, estimating a future corrosion amount from the obtained average corrosion progression, and diagnosing the corrosiveness of the environment is employed. The corrosion thickness of silver or copper can be measured by a method of using a metal test piece exposed for one month or can be measured with high degree of accuracy by a method of using a quartz crystal microbalance (QCM) sensor or an electric resistive type sensor intended for silver or copper. In ASHRAE (NPL 1), a corrosion thickness of silver correlated with a failure of an electronic device is employed as an environment diagnostic criterion.
The method of diagnosing an environment using the corrosion thickness of silver exposed for one month is also employed in ANSI/ISA 71.04 of NPL 2 in addition to ASHRAE.
Meanwhile, in ISO-11844-1 of NPL 3, an environment is diagnosed using a corrosion thickness of silver exposed for one year. Since most environments have seasonal variations, it is desirable to diagnose an environment using an annual corrosion thickness.
For the corrosion thickness of copper, a method of formulating influence of temperature, humidity, and corrosive gas which are corrosion factors and predicting the corrosion thickness of copper as disclosed in PTLs 1 and 2 may be used.
For the corrosion thickness of silver, as disclosed by the inventors of the present invention in PTL 3, a method of formulating influence of temperature, humidity, and corrosive gas which are corrosion factors in view of seasonal variations and predicting the corrosion thickness of silver may be used. The temperature, the humidity, and the corrosive gas vary greatly depending on a season in which a test piece is exposed and vary depending on operating conditions of an electronic device as well. In this regard, PTL 3 discloses a method for predicting an annual corrosion thickness of silver with a high degree of accuracy in view of variations in the temperature and the humidity (reducing sulfur which is corrosive gas is assumed to have constant density).
On the other hand, as disclosed in NPL 4, it is clear that relative humidity dependency of silver corrosion is unknown.
In NPL 5, the inventors of the present invention have proposed a mechanism of silver corrosion by atmospheric air including a hydrogen sulfide and a nitrogen dioxide and a corrosion prediction method thereof.